Power converter apparatus and method

ABSTRACT

A power converter apparatus comprises a set of switching elements communicatively coupled with a set of gate drive circuits. Each gate drive circuit is configured to provide a respective drive signal to a corresponding switching element, each switching element being switchably responsive to the respective drive signal. The apparatus includes a controller module configured to control an output state of the power converter, and selectively change one of a respective gate resistance and a respective gate current of a corresponding subset of the gate drive circuits based on the output state of the power converter.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with Government support under contract numberawarded by the National Aeronautics and Space Administration (NASA). TheGovernment has certain rights in the invention.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and benefit of U.S. patentapplication Ser. No. 17/401,402, filed Aug. 13, 2021, which isincorporated herein in its entirety.

TECHNICAL FIELD

This disclosure relates to a power converter and a method of operating apower converter, and more specifically to an active gate drive circuitfor a power converter.

BACKGROUND

Conventional power converters such as three-level active neutral-pointclamped (ANPC) converters, are employed to convert a direct current (DC)power to an alternating current (AC) power having a three-level output.These ANPC converters employ a set of switches to aid in the powerconversion. Typically, ANPC converters that employ silicon carbide (SiC)switches such as SiC metal-oxide-semiconductor field-effect transistors(MOSFETs) or insulated-gate bipolar transistors (IGBTs) are used when itis desirable to withstand a high voltage or high power. Each switch canbe operated or toggled by a respective gate drive circuit which canselectively provide a control signal to a gate terminal of the switch totransition the switch between conducting and non-conducting states.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present description, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which refers to the appended FIGS., inwhich:

FIG. 1 is a block diagram of a three-level ANPC converter, in accordancewith various aspects described herein.

FIG. 2 is a schematic diagram of a phase-leg of the ANPC converter ofFIG. 1 , in accordance with various aspects described herein.

FIG. 3 is a graphical representation of an example signal representingan output voltage of the phase-leg of FIG. 2 , in accordance withvarious aspects described herein.

FIG. 4 is a state diagram depicting transitions of an operating state ofthe phase-leg of FIG. 2 to generate the output voltage of FIG. 3 , inaccordance with various aspects described herein.

FIG. 5 depicts a conventional gate drive circuit.

FIG. 6 is a schematic diagram of a gate drive circuit in accordance withvarious aspects described herein.

FIG. 7 is a flow diagram of a method of operating a phase-leg of a powerconverter in accordance with various aspects described herein.

DETAILED DESCRIPTION

Aspects of the disclosure can be implemented in any environment,apparatus, or method for in a circuit regardless of the functionperformed by the circuit.

As used herein, the term “set” or a “set” of elements can be any numberof elements, including only one. Additionally, while terms such as“voltage”, “current”, and “power” can be used herein, it will be evidentto one skilled in the art that these terms can be interrelated whendescribing aspects of the electrical circuit, or circuit operations.Thus, as used herein, the term “power” can be representative of avoltage, a current, or both the voltage and current.

Connection references (e.g., attached, coupled, connected, and joined)are to be construed broadly and can include intermediate members betweena collection of elements and relative movement between elements unlessotherwise indicated. As such, connection references do not necessarilyinfer that two elements are directly connected and in fixed relation toeach other. In non-limiting examples, connections or disconnections canbe selectively configured to provide, enable, disable, or the like, anelectrical connection between respective elements. Non-limiting examplepower distribution bus connections or disconnections can be enabled oroperated by way of switching, bus tie logic, or any other connectorsconfigured to enable or disable the energizing of electrical loadsapplied to the bus. Additionally, as used herein, “electricalconnection” or “electrically coupled” can include a wired or wirelessconnection. The exemplary drawings are for purposes of illustration onlyand the dimensions, positions, order and relative sizes reflected in thedrawings attached hereto can vary.

As used herein, a “controller” or “module”, for example, “controllermodule”, or “switching module” can include a component configured oradapted to provide instruction, control, operation, or any form ofcommunication for operable components to affect the operation thereof.Such controllers or modules can include any known processor,microcontroller, or logic device, including, but not limited to: FieldProgrammable Gate Arrays (FPGA), a Complex Programmable Logic Device(CPLD), an Application-Specific Integrated Circuit (ASIC), a FullAuthority Digital Engine Control (FADEC), a Proportional Controller(PC), a Proportional Integral Controller (PI), a Proportional DerivativeController (PD), a Proportional Integral Derivative Controller (PID), ahardware-accelerated logic controller (e.g. for encoding, decoding,transcoding, etc.), the like, or a combination thereof. While describedherein as comprising separate elements, in non-limiting aspects suchcontrollers and modules can be incorporated on one or more devicesincluding a common device, such as a single processor ormicrocontroller. Non-limiting examples of such controllers or module canbe configured or adapted to run, operate, or otherwise execute programcode to effect operational or functional outcomes, including carryingout various methods, functionality, processing tasks, calculations,comparisons, sensing or measuring of values, or the like, to enable orachieve the technical operations or operations described herein. Theoperation or functional outcomes can be based on one or more inputs,stored data values, sensed or measured values, true or falseindications, or the like. While “program code” is described,non-limiting examples of operable or executable instruction sets caninclude routines, programs, objects, components, data structures,algorithms, etc., that have the technical effect of performingparticular tasks or implement particular abstract data types. In anothernon-limiting example, a controller module, or switching module can alsoinclude a data storage component accessible by the processor, includingmemory, whether transition, volatile or non-transient, or non-volatilememory. Additional non-limiting examples of the memory can includeRandom Access Memory (RAM), Read-Only Memory (ROM), flash memory, or oneor more different types of portable electronic memory, such as discs,DVDs, CD-ROMs, flash drives, Universal Serial Bus (USB) drives, thelike, or any suitable combination of these types of memory. In oneexample, the program code can be stored within the memory in amachine-readable format accessible by the processor. Additionally, thememory can store various data, data types, sensed or measured datavalues, inputs, generated or processed data, or the like, accessible bythe processor in providing instruction, control, or operation to affecta functional or operable outcome, as described herein.

Although various non-limiting aspects are depicted and described hereinusing various switching devices including MOSFETS or IGBTs or acombination thereof, other aspects are not so limited. Othernon-limiting aspects can include any desired switching device that canswitch a state between a low resistance state and a high resistancestate in response to an electrical signal. For example, the switchingdevices in various aspects can comprise, without limitation, any desiredtype of switching element including for example, transistors, gatecommutated thyristors, field effect transistors (FETs), IGBTs, MOSFETs,gate turn-off thyristors, static induction transistors, static inductionthyristors, or combinations thereof, and combinations thereof.

The exemplary drawings are for purposes of illustration only and thedimensions, positions, order and relative sizes reflected in thedrawings attached hereto can vary. Furthermore, the number of, andplacement of, the various components depicted in the Figures are alsonon-limiting examples of aspects associated with the disclosure. Forexample, while various components have been illustrated with relativeposition of etc., aspects of the disclosure are not so limited, and thecomponents are not so limited based on their schematic depictions.

A power converter is a power supply or power processing circuit thatconverts an input voltage waveform into a specified output voltagewaveform. Controllers associated with the power converters manage anoperation thereof by selectively controlling the conduction periods ofswitches employed therein. The switches employed by the power converterare typically semiconductor switching devices (e.g., MOSFETs, IGBTs,etc.).

In combination with the controller, a drive circuit (for example, a gatedrive circuit) is conventionally employed to selectively provide a drivesignal to a control terminal (e.g., a gate terminal) of eachsemiconductor switch to control an operation thereof in response to acommand signal (for example, a pulse-width modulated (PWM) signal) fromthe controller.

Conventional power converters, such as active neutral point clamped(ANPC) converters, are widely used in AC drives and flexible ACtransmission systems. When an ANPC converter is used, for example, in aninverter operation, a DC-link voltage can be converted into a variablealternating voltage and variable frequency. In contrast to aconventional half-bridge type converter having a two-level voltageoutput, ANPC converters can include an additional voltage level at theoutput. For example, the output voltage can include positive DC (DC+),negative DC (DC−), and can be a voltage output of zero or neutral.

Typical ANPC converters employ silicon carbide (SiC) switches such asMOSFETs when it is desirable to withstand a high voltage. As will beappreciated, SiC MOSFETs switch relatively faster in comparison to otherswitches, such as IGBTs, thereby resulting in relatively lower switchinglosses. However, the faster switching speed of the SiC MOSFETs can alsolead to higher voltage stress across the SiC MOSFETs employed inconventional ANPC converters due to a commutation loop inductance.

As will be described in detail herein, various non-limiting aspects ofan apparatus device and method for operating a phase-leg of a powerconverter such as an active neutral point clamped (ANPC) converter arepresented. Use of the apparatus and method can result in improvedoperating efficiency and operational life for an ANPC converter. Inparticular, the apparatus and methods enable selectively increasing anddecreasing a gate resistance of a gate drive circuit (for example a turnon resistance and a turn off resistance) for a correspondingsemiconductor switch of the ANPC converter, to thereby reduce voltagestresses, for example during a zero-cross of a PWM command signal to therespective gate drive circuit. Moreover, the apparatus and methodsenable selectively increasing or decreasing the switching speed of thesemiconductor switches of the ANPC converter based on a state or mode ofthe converter, to thereby reduce voltage stresses across the switches.Consequently, the life-time and the reliability of the ANPC convertercan be improved.

FIG. 1 is a block diagram of a three-level ANPC power converter 100, inaccordance with aspects of the present disclosure. In non-limitingaspects, the power converter 100 can comprise an inverter that operatesto convert a direct current (DC) power to an alternating current (AC)power. In an aspect, the power converter 100 includes an input port 102,an output port 104, and a set of phase-legs 106, 108, 110 disposedbetween the input port 102 and the output port 104. Additionally, thepower converter 100 can also include a modulator 112 communicativelycoupled to the set of phase-legs 106, 108, 110.

The input port 102 can include a positive input terminal 114, a neutralinput terminal 116, and a negative input terminal 118. The positiveinput terminal 114, neutral input terminal 116, and negative inputterminal 118 can be hereinafter collectively referred to as inputterminals 114-118. The positive input terminal 114 can be maintained ata positive voltage, the negative input terminal 118 can be maintained ata negative voltage, and the neutral input terminal 116 can be maintainedat a neutral voltage. In non-limiting aspects, the positive voltage andthe negative voltage can be non-zero potentials while the neutralvoltage can be a zero potential or substantially close to a zeropotential. In some aspects, the neutral voltage can also be a non-zeropotential. The input terminals 114-118 are electrically coupled to inputterminals (see FIG. 2 ) of each of the phase-legs 106-110.

In the example of FIG. 1 , a three-phase output voltage can be availableat the output port 104 of the power converter 100. The output port 104includes output terminals 120, 122, 124 to supply the three-phase outputvoltage to any target electronic device (not shown) or load coupled tothe power converter 100. More particularly, a single-phase voltage canbe supplied via each of the output terminals 120, 122, 124. These outputterminals 120, 122, 124 can be hereinafter collectively referred to asoutput terminals 120-124. In some aspects, output terminals 120-124 ofthe output port 104 are electrically coupled to an output terminal (seeFIG. 2 ) of each of the phase-legs 106-110. The output voltage at eachof the output terminals 120-124 includes three levels such as a firstlevel, a second level, and a neutral level.

By way of example, the first level can be a positive voltage level,while the second level can be a negative voltage level. By way ofanother example, while the first level can be the negative voltagelevel, the second level can be the positive voltage level. Moreover, theneutral level can be a zero voltage or substantially close to a zerovoltage. In certain aspects, the neutral level can be a non-zerovoltage.

The phase-legs 106, 108, 110 are electrically coupled to the input port102 and the output port 104. Each of the phase-legs 106, 108, 110 isconfigured to convert the DC power received from the input port 102 toan AC power and supply the generated AC power to the output port 104 asa phase voltage and a phase current. More particularly, the phase-legs106, 108, 110 are coupled to a corresponding output terminal 120, 122,124 to provide the generated AC power thereto. In some aspects, one ormore of the phase-legs 106-110 can include a set of switches (see FIG. 2) arranged to switchably convert the DC power to the AC power.

The modulator 112 is communicatively coupled to the phase-legs 106-110.In the non-limiting aspect illustrated in FIG. 1 , the modulator 112 isdepicted as a part of the power converter 100. In other aspects, themodulator 112 can be disposed remote from the power converter 100. Insome aspects, the modulator 112 can include a controller module 126configured to control operations of the phase-leg 106-110 to facilitatethe conversion of the DC power to the AC power by the phase-legs106-110. The controller module 126 can include hardware elements such asa specially programmed general-purpose computer, an electronic processorsuch as a microprocessor, a digital signal processor, an FPGA, amicrocontroller, or combinations thereof. Further, the controller module126 can include input/output ports (I/O) and a storage medium, such asan electronic memory. Various examples of the microprocessor include,but are not limited to, a reduced instruction set computing (RISC)architecture type microprocessor or a complex instruction set computing(CISC) architecture type microprocessor. Further, the microprocessor canbe a single-core type or multi-core type. Alternatively, the controllermodule 126 can be implemented using hardware elements such as circuitboards with processors, logic gates, or as software running on aprocessor such as a personal computer (PC), or a microcontroller.

The controller module 126 can be communicatively coupled to thephase-legs 106-110. More particularly, the controller module 126 can becommunicatively coupled to the respective switches 210-220 (see FIG. 2 )of the phase-legs 106-110 and configured to selectively controlswitching of the switches 210-220 to facilitate conversion of the DCpower to the AC power. As will be described in more detail herein, thecontroller module 126 can be configured to operate the phase-legs106-110 such that the respective switching speed of the switches 210-220of the phase-legs 106-110 is selectively adjusted based on the outputstate of a respective phase-leg 106-110 of the power converter 100,consequently resulting in a reduction in the voltage stress on theswitches 210-220 of the phase-legs 106-110.

It can be noted that use of the three phase-legs 106-110 in the powerconverter 100 aids in generating a three-phase output at the output port104. It will be appreciated that although the power converter 100 ofFIG. 1 is shown as having the three phase-legs 106-110, other aspectsare not so limited, and use of a power converter having less than threephase-legs or greater than three phase-legs is also contemplated. Forexample, a power converter with one phase-leg can produce a single-phaseoutput voltage. By way of another non-limiting example, a powerconverter with two phase-legs can produce a two-phase output voltage.

Referring now to FIG. 2 , a schematic diagram of one non-limiting aspectof a phase-leg 200, such as the phase-leg 106 of the power converter 100of FIG. 1 , in accordance with aspects of the present disclosure, isshown. In some aspects, other phase-legs, such as phase-legs 108 and 110can also have a configuration similar to the configuration of thephase-leg 200 depicted in FIG. 2 . Also, FIG. 2 will be described withreference to the components of FIG. 1 .

In some aspects, the phase-leg 200 can include a set of input terminalssuch as a first input terminal 202, a second input terminal 204, and aneutral input terminal 206. The phase-leg 200 can also include a firstset of switches 209 and an output terminal 208. The first set ofswitches 209 can include a first switch 210, a second switch 212, athird switch 214, a fourth switch 216, a fifth switch 218, and a sixthswitch 220. The first switch 210, second switch 212, third switch 214,fourth switch 216, fifth switch 218, and sixth switch 220 canhereinafter collectively be referred to as switches 210-220. The firstset of switches 209 can also include a set of corresponding gate drivecircuits 250. For example, a respective gate drive circuit 250 can becommunicatively coupled to each switch 210-220. For example, arespective gate drive circuit 250 can be communicatively coupled to agate terminal of each respective switch 210-220. The set of gate drivecircuits 250 can be communicatively coupled to the controller module 126of the modulator 112 to receive a command signal (e.g., a PWM voltagesignal) therefrom.

Although not depicted in FIG. 2 , the first input terminal 202, thesecond input terminal 204, and the neutral input terminal 206 of thephase-leg 200 can be respectively communicatively coupled to thepositive input terminal 114, the negative input terminal 118, theneutral input terminal 116 of the power converter 100 of FIG. 1 . Also,the output terminal 208 of the phase-leg 200 can be communicativelycoupled to the output terminal 124 of the power converter 100 of FIG. 1. Furthermore, a respective gate terminal of each of the switches210-220 can be operatively coupled to the modulator 112 of the powerconverter 100. More particularly, the gate terminal of each of theswitches 210-220 can be communicatively coupled to the controller module126 of the modulator 112.

For ease of description and understanding, FIG. 2 depicts onenon-limiting aspect of the phase-leg 200 having six switches 210-220.However, aspects having the phase-leg 200 comprising greater than six orfewer than six switches are also contemplated. Moreover, in thenon-limiting aspect of FIG. 2 , the switches 210-216 are discussed anddescribed as comprising SiC MOSFETs, and the switches 218-220 arediscussed and described as comprising IGBTs, wherein each switch 218-220can include a semiconductor switch element and an anti-parallel diode.Other aspects are not so limited and the phase-leg 200 having othertypes of switches is also contemplated. Other non-limiting examples ofthe switches 210-220 can include transistors, gate commutatedthyristors, FETs, MOSFETs, IGBTs, gate turn-off thyristors, staticinduction transistors, static induction thyristors, or combinationsthereof. Furthermore, materials used to form the switches 210-220 caninclude, but are not limited to, silicon (Si), germanium (Ge), SiC,gallium nitride (GaN), or combinations thereof.

As will be appreciated, a SiC switch module (e.g., a MOSFET) can includemore than one switch. Therefore, in some non-limiting aspects, threesuch SiC modules can be used to form the phase-leg 200 of FIG. 2 . Byway of example, a first SiC switch module (not shown) can comprise thefirst and second switches 210 and 212, a second SiC switch module (notshown), can comprise the third and fourth switches 214 and 216, and athird IGBT switch module (not shown) can comprise the fifth and sixthswitches 218 and 220. It will be appreciated that other types of switchmodules can also be used without limiting the scope of the presentdisclosure.

As depicted in the non-limiting aspect of FIG. 2 , the first switch 210,the second switch 212, the third switch 214, and the fourth switch 216can be coupled electrically in series. More particularly, the switches210-216 can be coupled electrically in series such that a sourceterminal of the first switch 210 is connected to a drain terminal of thesecond switch 212, a source terminal of the second switch 212 isconnected to a drain terminal of the third switch 214, and a sourceterminal of the third switch 214 is connected to a drain terminal of thefourth switch 216.

Further, the first switch 210 is operatively coupled to the first inputterminal 202 and the fourth switch 216 is operatively coupled to thesecond input terminal 204. More particularly, as depicted in FIG. 2 , adrain terminal of the first switch 210 can be connected to the firstinput terminal 202, while a source terminal of the fourth switch 216 canbe connected to the second input terminal 204.

Furthermore, a first node 226 represents an interconnection point of thesecond switch 212 and the third switch 214. The first node 226 iscommunicatively coupled to the neutral input terminal 206. Also,reference numeral 228 represents a node or interconnection point of thefirst switch 210 and the second switch 212. The fifth switch 218 iscommunicatively coupled between the node 228 and the output terminal208. More particularly, in the non-limiting example of FIG. 2 , acollector terminal of the fifth switch 218 is connected to the node 228and an emitter terminal of the fifth switch 218 is connected to theoutput terminal 208. Moreover, reference numeral 230 represents a nodeor interconnection point of the third switch 214 and the fourth switch216. The sixth switch 220 is communicatively coupled between the node230 and the output terminal 208. In particular, an emitter terminal ofthe sixth switch 220 is connected to the node 230 and a collectorterminal of the sixth switch 220 is connected to the output terminal208.

Moreover, in some aspects, the phase-leg 200 can also include capacitors222 and 224. The capacitor 222 is connected between the first inputterminal 202 and the neutral input terminal 206. Also, the capacitor 224is connected between the second input terminal 204 and the neutral inputterminal 206.

The controller module 126 can be configured to operate the phase-leg 200in one or more operating states including, but not limited to, a neutralstate, a first intermediate neutral state, a first state, a secondintermediate neutral state, or a second state (see FIG. 4 ).

In some aspects, the phase-leg 200, when operated in any of the neutralstate, the first intermediate neutral state, or the second intermediateneutral state, can be configured to generate an output voltage havingthe neutral level at the output terminal 208. Moreover, the phase-leg200, when operated in the first state, can be configured to generate theoutput voltage having the first level at the output terminal 208. In asimilar fashion, the phase-leg 200, when operated in the second state,can be configured to generate the output voltage having the second levelat the output terminal 208. A signal representative of an example outputvoltage of the phase-leg 200 is depicted in FIG. 3 .

To transition the state of the phase-leg 200 between the neutral state,the first intermediate neutral state, the first state, the secondintermediate neutral state, and the second state, the controller module126 can be configured to selectively operate one or more of the switches210-220 in a conducting state and operate the remaining switches in anon-conducting state. As will be appreciated, the switches operated inthe conducting state allow an electrical current to pass through, whilethe switches operated in the non-conducting state block a flow of theelectrical current therethrough.

The controller module 126 can be configured to operate the switches210-220 in the conducting state or the non-conducting state by providinga command signal (e.g., a PWM command signal) to the respective gatedrive circuit 250 of that switch 210-220.

In the aspect of FIG. 2 , the switches 210-216 are depicted as N-channelSiC MOSFETs, and the switches 218-220 are depicted as IGBTs.Accordingly, to operate any of the switches 210-220 in the conductingstate, it is desirable to supply a control or drive signal having ahigher magnitude (H) to a corresponding gate terminal. It can be notedthat the control or drive signal having the higher magnitude isrepresentative of a control or drive signal having a magnitude that isgreater than a magnitude of a signal provided to a corresponding sourceor emitter terminal. Similarly, to operate any of the switches 210-220in the non-conducting state, it is desirable to supply a control ordrive signal having a lower magnitude (L) to the corresponding gateterminal. It can be noted that the control signal having the lowermagnitude is representative of a control or drive signal having amagnitude that is lower than a magnitude of a signal provided to acorresponding source or emitter terminal. Moreover, it can be noted thatif P-channel SiC MOSFETs are used as the switches 210-220, the levels ofthe control signals can be interchanged.

Accordingly, to operate any of the switches 210-220 in the conductingstate, the controller module 126 can be configured to supply a drivesignal via the respective gate drive circuit 250 having the highermagnitude to the gate terminals of the respective switches 210-220.Similarly, to operate any of the switches 210-220 in the non-conductingstate, the controller module 126 can be configured to supply a drivesignal via the gate drive circuit 250 having the lower magnitude (L) tothe gate terminals of the respective switches 210-220.

FIG. 3 is a graphical representation 300 depicting an example signalthat represents an output voltage 302 of a phase-leg such as thephase-leg 200, in accordance with aspects of the present disclosure.FIG. 3 is described with reference to the components of FIG. 2 .

The output voltage 302 can be obtained at the output terminal 208 of thephase-leg 200. Reference numeral 304 represents an X-axis and thereference numeral 306 represents a Y-axis. The X-axis 304 and the Y-axis306 respectively represent time and an amplitude of the output voltage302. Further, reference numerals 308, 310, and 312 represent a firstlevel, a second level, and a neutral level, respectively, of the outputvoltage 302. Moreover, reference numerals 314 and 316 respectivelyrepresent a first cycle and a second cycle of the output voltage 302.For ease of illustration, two cycles (i.e., the first and second cycles314, 316) of the output voltage 302 are represented in FIG. 3 . It willbe appreciated that output voltage 302 can include more than two cycles.Further, in the example of FIG. 3 , the first cycle 314 is shown as apositive cycle while the second cycle 316 is shown as a negative cycle.Other aspects are not so limited, and in other aspects, the phase-leg200 can generate the output voltage 302 having any number of firstcycles 314, any number of second cycles 316, or any combination orpattern of the first and second cycles 314, 316. Moreover, use of thephase-leg 200 to generate the output voltage 302 having only the firstcycles 314 or only the second cycles 316 is also contemplated.

In FIG. 3 , T₀₁ represents a total time corresponding to a firstintermediate neutral state of the phase-leg 200, T 02 represents a totaltime corresponding to a second intermediate neutral state of thephase-leg 200, T N represents the total time of the neutral state, Tmin,represents a minimum pulse duration corresponding to any of the first,second, and third levels 308, 310, 312 of the output voltage 302, and Tsrepresents a time period of a single cycle such as the first cycle 314or the second cycle 316 of the output voltage 302 of the phase-leg 200.

FIG. 4 is a state diagram 400 depicting transitions of an operatingstate of the phase-leg 200 of FIG. 2 to generate the output voltage 302of FIG. 3 , in accordance with aspects of the present specification.FIG. 4 is described in conjunction with FIGS. 2 and 3 . The output oroperating states can comprise the neutral state 402, the firstintermediate neutral state 404, the first state 406, the secondintermediate neutral state 408, and the second state 410. The arrows areused to generally indicate a non-limiting subsequent operating statecorresponding to a given operating state, with a double-headed arrowused to generally indicate a transition from a given operating state toa non-limiting subsequent operating state can occur in either direction.

During operation of the phase-leg 200, at time t=0, if it is assumedthat the phase-leg 200 is operating in the neutral state 402 and theoutput voltage 302 having the first level 308 is desired as depicted inthe first cycle 314, the controller module 126 is configured totransition the phase-leg 200 to the first intermediate neutral state 404and subsequently to the first state 406. Further, the controller module126 can be configured to maintain the phase-leg 200 in the first state406 for a first predetermined time duration. The first predeterminedtime duration can be computed by the controller module 126 based on adesired frequency and duty-cycle of the output voltage 302.

In a non-limiting aspect, subsequent to the lapse of the firstpredetermined time duration, the controller module 126 can be configuredto transition the phase-leg 200 back to the neutral state 402. In otheraspects, as depicted in FIG. 4 , the controller module 126 can beconfigured to transition the phase-leg 200 directly to the neutral state402 from the first state 406. In other aspects, as indicated by thedouble headed arrows, in FIG. 4 , the controller module 126 can beconfigured to transition the phase-leg 200 to the neutral state 402 fromthe first state 406 via the first intermediate neutral state 404.

Moreover, to generate the output voltage 302 having the second level310, the controller module 126 can be configured to transition thephase-leg 200 to second intermediate neutral state 408 and subsequentlyto the second state 410. Further, the controller module 126 can beconfigured to maintain the phase-leg 200 in the second state 410 for asecond determined time duration. The second determined time duration canbe computed by the controller module 126 based on a desired frequencyand duty-cycle of the output voltage 302. Subsequent to the lapse of thesecond determined time duration, the controller module 126 can beconfigured to transition the phase-leg 200 back to the neutral state402. In one aspect, as depicted in FIG. 4 , the controller module 126can be configured to transition the phase-leg 200 directly to theneutral state 402 from the second state 410. Alternatively, as indicatedby the double headed arrows in FIG. 4 , the controller module 126 can beconfigured to transition the phase-leg 200 to the neutral state 402 fromthe second state 410 via the second intermediate neutral state 408.

Table 1 illustrates levels of the output voltage 302 corresponding tothe operating states 402-410, and the corresponding condition of theswitches 210-220 of FIG. 2 . As will be understood, the respective stateof each switch 210-220 is illustrated in Table 1 by a numeral “1” or“0”, wherein the numeral “1” is indicative of a switch 210-220 that isin an “ON” or conducting state, and the numeral “0” is indicative of aswitch 210-220 that is in an “OFF” or non-conducting state. depicted ashaving a state of “1”, and a switch 210-220.

TABLE 1 Operating State of Switch Condition Converter Output Phase-leg200 210 212 214 216 218 220 Voltage State Off 0 0 0 0 0 0 Off First Int.Neutral 404 0 1 0 0 1 0 Neutral level 312 First state 406 1 0 1 0 1 0First level 308 Second Int. Neutral 408 0 0 1 0 0 1 Neutral level 3122nd state 410 0 1 0 1 0 1 Second level 310 Neutral 402 0 1 1 0 1 1Neutral level 312

Some ANPC converters can employ a hybrid switching arrangement, forexample having a set of IGBTs as the switching devices at the AC outputside of the converter. For example, employing a respective IGBT in lieuof a MOSFET for the fifth switch 218 and sixth switch 220. In suchcases, when the output voltage of the converter changes polarity, (e.g.,after turn-off of an IGBT), minority carriers can remain or be stored inan N-drift region of the IGBT device. When a voltage is subsequentlyapplied across the IGBT device before a charge recombination is complete(e.g., at a fast switching speed), the remaining or stored minoritycarriers flow out, causing a “current bump” in the device. The “currentbump” flowing in the IGBT device and a large commutation loop can causea high voltage stress across the IGBT device. Similarly, the reverserecovery of the silicon diode can cause high voltage stress across theIGBT device after a polarity change of the output voltage.

To reduce such high voltage stresses across the fifth switch 218 andsixth switch 220, the gate resistance of the other switches (e.g.,switches 210-216) can be increased. However, the increased gateresistance value would be higher than necessary during periods whenthere is no polarity change of the PWM voltage signal command. Thus,simply increasing the gate resistance of the switches 210-220 of thefirst set of switches 209 to reduce voltage overshoot across the fifthswitch 218 and sixth switch 220 would result in increased switching lossof the remaining switches 210-216, and reduce the converter 200operating efficiency.

For example, FIG. 5 , depicts a schematic diagram of a conventional gatedrive circuit. Typically, the gate drive circuit includes complimentaryfirst and second switches Q1, Q2, for example embodied in a N-channelMOSFET and a P-channel MOSFET, respectively, with coupled gateterminals. A command signal Sc (e.g., a PWM signal) is provided to thejunction “S1” coupling the gate terminals of the first and secondSwitches Q1, Q2, of the gate drive circuit. A drive signal Sd isprovided to the junction “S2” coupling the drain terminals of the firstand second Switches Q1, Q2. In a typical power converter, the firstswitch Q1, and second switch Q2 can be connected between power terminalsto define a positive actuation potential (designated “+V”), and anegative actuation potential (designated “−V”). The positive andnegative actuation potentials+V, −V are respective actuation potentialsreferenced to the electrical potential on the junction S1. The switchesQ1, Q2 can be MOSFETS, and can be respectively selectively actuated inresponse to the input signal Spwm. When the upper switch Q1 is in an“ON” condition (i.e., conducting) and the lower switch Q2 is in an “OFF”condition (i.e., non-conducting), the drive signal Sd is at the positiveactuation potential V, and a gate charging current flows in thedirection illustrated by arrow “Io”. When the lower switch Q2 is in anON condition, and the upper switch Q1 is in an OFF condition, the drivesignal output Sd is at the negative actuation potential −V or zero, anda discharge current flows in the opposite direction to the oneillustrated by arrow “To”. The value of the charge and discharge currentIo will be dependent on the value of the resistors R1 and R2respectively, sometimes called a “turn-on resistor” R1 and a “turn-offresistor” R2.

During switching operations, the switching behavior (e.g., a switchingspeed) of each switch Q1, Q2 can typically be defined at least in partby the respective resistance value of the turn-on resistor R1, orturn-off resistor R2, respectively. The turn-on resistor R1 or turn-offresistor R2 are typically embodied in resistors having a predeterminedfixed resistance value, and are coupled to the drain or source terminalof each switch Q1, Q2, respectively. Conventional turn-on and turn-offresistors R1, R2 can have resistance values selected based on a desiredswitching speed or dive signal output Sd. The turn-on and turn-offresistors R1, R2 can also limit the magnitude of the output current Ioand protect the corresponding switch Q1, Q2 from voltage transients thatcan damage the switch Q1, Q2 (e.g., an avalanche breakdown). Forexample, using a relatively large resistance value for the turn-onresistor R1 and turn-off resistor R2 can provide an increased degree(relative to lower resistance values) of voltage transient protection,but will slow the rate of charge or discharge of the respective inputcapacitance of each switch Q1, Q2, and thereby result in a slowerswitching speed of each switch Q1, Q2. Conversely, using a relativelysmall resistance value for the turn-on resistor R1 and turn-off resistorR2 can provide a relatively lower degree (relative to higher resistancevalues) of voltage transient protection, but will speed the rate ofcharge or discharge of the respective input capacitance of thesemiconductor switch being driven by the gate drive circuit, and therebyresult in a relatively faster switching speed than when arranged withrelatively higher resistance values for turn-on resistor R1 and turn-offresistor R2. The value of each turn-on resistor R1 and turn-off resistorR2 is typically selected or predetermined based on a calculatedworst-case condition and is not optimized for switching speed in alloutput states or operating conditions of the converter. Thus,conventional gate drive circuits have a relatively large resistancevalue of the turn-on resistor R1 and turn-off resistor R2 value in alloperating states of the converter, which can result in less than optimalswitching speeds and switching losses.

FIG. 6 illustrates a non-limiting example of a gate drive circuit 250 inaccordance with an aspect. For example, the gate drive circuit 250 cancorrespond to a switch 210-220 of a respective phase-leg 200 of thepower converter 100. In such aspects, responsive to a respective commandsignal 53 from the controller module 126, each gate drive circuit can beconfigured to selectively operate the corresponding switch 210-220. Forease of description an understanding, FIG. 6 is depicted showing only onswitch 210, with the other switches 212-220 omitted for clarity. It willbe appreciated that references to switch 210 operation can berespectively applied to switches 212-220. As will be described in moredetail herein, the gate drive circuit 250 can be configured toselectively adjust or modify one of a resistance (e.g., a gateresistance 80, 90) and a current (e.g., a gate current Ig) to thecorresponding switch 210 based on an output state 402, 404, 406, 408,410 of the respective phase-leg 200. The controller module 126 can becommunicatively coupled with a set of sensors 40 or other source of dataassociated with the operation of the power converter 100. For example,the set of sensors 40 can include a temperature sensor 41 configured toprovide information indicative of an operation temperature associatedwith the operation of the power converter 100, a current sensor 42configured to provide information indicative of an electrical currentassociated with the operation of the power converter 100, or a voltagesensor 43 configured to provide information indicative of an voltageassociated with the operation of the power converter 100, or acombination thereof. The set of sensors 40 can include a switch sensor44 configured to provide information indicative of an status of acorresponding switch 210-220 of the phase-leg 200, Accordingly, the gatedrive circuit 250 can be configured to selectively adjust or modify oneof a gate resistance 80, 90 and a gate current Ig to the correspondingswitch 210 based on a output state of the respective phase-leg 200, atleast one of temperature data, current data, voltage data, or a switch210 status, or a combination thereof, provided to the controller module126. For ease of description, the gate drive circuit 250 of FIG. 6 isdepicted as communicatively coupled to the first switch 210, it will beappreciated that in other aspects, a respective gate drive circuit 250can likewise be communicatively coupled to the remaining switches210-220 of a phase-leg 200. For example, non-limiting aspects of aphase-leg 200 can include a set of switching elements 209communicatively coupled with a set of gate drive circuits 250. Each gatedrive circuit 250 can be configured to provide a respective gate drivesignal to a corresponding switch 210-220, each switch 210-220 beingswitchably responsive to the respective drive signal. Such powerconverters 100 can include a controller module 126 configured to controlan output state 402, 404, 406, 408, 410 of the power phase-leg 200, andselectively change one of a respective resistance 80, 90 and a gatecurrent Ig of a corresponding subset of the gate drive circuits 250based on the output state 402, 404, 406, 408, 410 of the phase-leg 200.

The gate drive circuit 250 can include a gate drive circuit input side51 and a gate drive circuit output side 52. The gate drive circuit 250can further include a second set of gate control switches 60, includinga first gate control switch 61, and a second gate control switch 62, anda third set of gate control switches 70 including a first speed controlswitch 71 and a second speed control switch 72. The gate drive circuit250 can further include a first set of resistors 80, a second set ofresistors 90, and a third set of resistors 99. The first set ofresistors 80 can include a first resistor 81 and a second resistor 82.The second set of resistors 90 can include a third resistor 93 and afourth resistor 94 arranged electrically in parallel with the firstresistor 81 and second resistor 82, respectively. The third set ofresistors 99 can include a fifth gate resistor 105 and a sixth gateresistor 107. A voltage source 56 can be coupled to the gate drivecircuit 250 to provide a control voltage such as a first control voltageVc1 and a second control voltage Vc2, to the second set of gate controlswitches 60 via the first set of resistors 80. The third set of gatecontrol switches 70 can further selectively additionally provide thefirst control voltage Vc1 and second control voltage Vc2 via the secondset of resistors 90. The gate drive circuit input side 51 can becommunicatively coupled via an input node 54 to the controller module126. In non-limiting aspects, the first gate terminal 64 can becommunicatively coupled to the input node 54 via the fifth gate resistor105, and the second gate terminal 67 can be communicatively coupled tothe input node 54 via the sixth gate resistor 107. The controller module126 can be configured to provide a command signal 53, such as a PWMsignal to the input node 54. The first gate control switch 61, and thesecond gate control switch 62 can be respectively selectively actuatedin response to the command signal 53. The gate drive circuit output side52 can be communicatively coupled, via a gate drive circuit output node55, to a signal input terminal 201 (e.g., a gate terminal) of thecorresponding switch 210 to provide a gate drive signal 57 thereto tothereby operate or drive the corresponding switch 210.

In non-limiting aspects, the first gate control switch 61 can comprise aMOSFET-type switch, having a first source terminal 65, a first gateterminal 64, and a first drain terminal 63. In non-limiting aspects thesecond gate control switch 62 can comprise a MOSFET-type switch, havinga second source terminal 66, a second gate terminal 67, and a seconddrain terminal 68. The first gate control switch 61 and second gatecontrol switch 62 can be coupled at the gate drive circuit output node55. For example, as depicted, the first source terminal 65 and secondsource terminal 66 can be communicatively coupled to the gate drivecircuit output node 55. In non-limiting aspects, the first gate terminal64 and second gate terminal 67 can be communicatively coupled to theinput node 54 via the fifth gate resistor 105 and sixth gate resistor107, respectively.

In the example illustrated, when the first gate control switch 61 is inan “ON” condition (e.g., conducting) and the second gate control switch62 is in an “OFF” condition (e.g., non-conducting), the command signal53 is at the positive actuation potential Vc1, and a charging or gatecurrent Ig flows in the direction illustrated by the arrow “Ig”.Conversely, when the second gate control switch 62 is in an ONcondition, and the first gate control switch 61 is in an OFF condition,the gate current Ig is at the negative actuation potential Vc2, and adischarge current flows in the opposite direction to the one indicatedby the arrow “Ig”.

As will be described in more detail herein, depending on the state ofthe first speed control switch 71 and second speed control switch 72,the value of the gate current Ig (e.g., a charging or dischargingcurrent) can be dependent on the value of the first resistor 81 andthird resistor 93, (i.e., a turn-on resistance) and the value of thesecond resistor 82 and fourth resistor 94, (i.e., a turn-on resistance).

The positive and negative actuation potentials Vc1, Vc2 are respectiveactuation potentials referenced to the electrical potential on the inputnode 54. The first gate control switch 61 can be communicatively coupledto the voltage source 56 receive the first control voltage Vc1 via thefirst resistor 81. In non-limiting aspects, the first control voltageVc1 can be a positive DC voltage. The second gate control switch 62 canbe communicatively coupled to the voltage source 56 to receive thesecond control voltage Vc2 via the second resistor 82. In non-limitingaspects, the second control voltage Vc2 can be a negative DC voltage. Inaspects, the first gate control switch 61 can be configured toselectively switch or toggle to an ON or conductive state when thecommand signal 53 (e.g. a PWM signal) is a positive voltage. The firstgate control switch 61 can additionally be configured to selectivelyswitch or toggle to an OFF or non-conductive state when the commandsignal 53 is a negative voltage. Conversely, the second gate controlswitch 62 can be configured to selectively switch or toggle to an ON orconductive state when the command signal 53 is a negative voltage. Thesecond gate control switch 62 can additionally be configured toselectively switch or toggle to an OFF state when the command signal 53is a positive voltage.

For ease of description and understanding, the switches of the secondset of gate control switches 60 and third set of gate control switches70 are generally described as comprising MOSFET type switches. However,other aspects are not so limited, and the switches of the second set ofgate control switches 60 and third set of gate control switches 70 cancomprise any desired type of switching device. In non-limiting aspects,the switches the second set of gate control switches 60 and third set ofgate control switches 70 can comprise any desired switching device thatcan switch a state between a low resistance or ON state (conducting) anda high resistance or OFF state (non-conducting) in response to anelectrical signal. For example, the switches of the second set of gatecontrol switches 60 and third set of gate control switches 70 in variousaspects can comprise, without limitation, any desired type of switchingelement such as, MOSFETs, JFETs, IGBTs, gate commutated thyristors,field effect transistors (FETs), IGBTs, MOSFETs, gate turn-offthyristors, static induction transistors, static induction thyristors,or combinations thereof without departing from the scope of thedisclosure.

In non-limiting aspects, the first resistor 81 can be coupled in serieswith the first drain terminal 63 of the first gate control switch 61,and the second resistor 82 can be coupled in series with the seconddrain terminal 68 of the second gate control switch 62. The respectiveresistance value (e.g., in ohms) of the first resistor 81 and the secondresistor 82 can be predetermined resistance values to provide anoptimized switching speed of the switch 210, when the output state 402,404, 406, 408, 410 of the corresponding phase-leg 200 comprises either afirst state having a first output voltage, or a second state having asecond output voltage.

As discussed hereinabove, the controller module 126 can be configured tooperate the phase-leg 200 in one or more operating states including, butnot limited to, a neutral state, a first intermediate neutral state, afirst state, a second intermediate neutral state, or a second state (seeFIG. 4 ). Accordingly, the controller module 126 can be furtherconfigured to selectively actuate, toggle, or otherwise operate thethird set of gate control switches 70 based on the operating state ofthe phase-leg 200.

For example, when the operating condition of the phase-leg 200 is suchthat phase-leg state transitions are between the first state and thefirst intermediate neutral state (e.g., a positive output voltage), orphase-leg state transitions are between the second state and the secondintermediate neutral state (e.g., a negative output voltage), thecontroller module 126 can be configured to close, or maintained in aclosed condition (i.e., in an “ON”, or conducting state) the switches ofthe third set of gate control switches 70. In this arrangement, thethird resistor 93 and fourth resistor 94 are operatively coupled to thecircuit, in parallel with the first resistor 81 and second resistor 82,respectively. Accordingly, the charge and discharge currents for theswitch 210 are thereby increased based at least on the reduced turn-onresistance of the parallel combination of the first resistor 81 andthird resistor 93, and the reduced turn-off resistance of the parallelcombination of the second resistor 82 and fourth resistor 94,respectively.

In another non-limiting example, when the controller module 126 isoperating the phase-leg 200 to change the phase-leg output voltagepolarity, the controller module 126 can be further configured toselectively actuate, toggle, or otherwise operate the third set of gatecontrol switches 70 based on the operating state of the phase-leg 200.For example, when the phase-leg 200 output voltage is transitioning froma second level (e.g., a negative voltage) via a neutral level to a firstlevel (e.g., a positive voltage), the controller module 126 can beconfigured to open, toggle, or otherwise maintain the first speedcontrol switch 71 to an “OFF” or non-conducting state. In thisarrangement, the third resistor 93 and fourth resistor 94 are notoperatively in the circuit 250. Accordingly, the charge and dischargecurrent for the switch 210 are thereby reduced based at least on theincreased turn-on resistance of the first resistor 81 and the increasedturn-off resistance of the second resistor 82 with the parallel circuitcontribution of the third resistor 93 and fourth resistor 94,respectively, removed.

With this arrangement, a relatively large resistance value for theturn-on resistance and turn-off resistance can be selectively provided,based on the state of the phase-leg 200, to provide an increased degreeof voltage transient protection, but will only result in a relativelyslower switching speed of the driven switch 210-220 for briefpredetermined or selective time periods. Conversely, with thisarrangement, a relatively small resistance value for the turn-onresistance and turn-off resistance can be selectively provided, based onthe state of the phase-leg 200, to provide a relatively faster switchingspeed for relatively longer predetermined or selective time periods. Inthis way, the value of each turn-on resistance and turn-off resistancecan be selected or predetermined based on a desired optimized operationfor switching speed in all output states 402, 404, 406, 408, 410 oroperating conditions of the phase-leg 200.

While various non-limiting aspects have been described for ease ofunderstanding, with reference to FIG. 6 , with the first set of speedcontrol switches 70 comprising the first speed control switch 71, andthe second speed control switch 72, and the second set of resistors 90comprising the third resistor 93 and the fourth resistor 94 arrangedelectrically in parallel with the first resistor 81 and second resistor82, respectively, other aspects are not so limited. In othernon-limiting aspects any number of switching arrangements, and anydesired number of resistors, having any desired respective resistancevalue can be employed without departing from the scope of the disclosureherein. For example, it is contemplated that other non-limiting aspectsthe first set of speed control switches 70 can comprise a plurality offirst speed control switches 71, and the second set of resistors 90 cancomprise a plurality of third resistors 93 respectively arranged inseries with each other, and in parallel with the first resistor 81.Likewise, it is contemplated that other non-limiting aspects, the firstset of speed control switches 70 can comprise a plurality second speedcontrol switches 72, and the second set of resistors 90 can comprise aplurality of fourth resistors 94 respectively arranged in series witheach other, and in parallel with the second resistor 82.

In such aspects, each of the plurality of third resistors 93 andplurality of fourth resistors 94 can have a predetermined resistancevalue. The predetermined resistance value of each third resistor 93 andfourth resistor 94 can be the same value as the other resistors in theplurality of second resistors 93, and the plurality of fourth resistors94, respectively. In other aspects, the predetermined resistance valueof each third resistor 93, and fourth resistor 94 can be a differentresistance value from the other resistors in the plurality of secondresistors 93, and the plurality of fourth resistors 94, respectively. Itis further contemplated that in various aspects, depending on the stateof the phase-leg 200, one or more speed control switches 71 of theplurality of first speed control switches 71, or one or more speedcontrol switches 72 of the plurality of second speed control switches 72can be selectively operated to provide a predetermined turn-onresistance or turn-off resistance. That is, with such arrangements, apredetermined relatively large resistance value for the turn-onresistance and turn-off resistance can be selectively provided using oneor more resistors, based on at least the state of the phase-leg 200, toprovide an increased degree of voltage transient protection. Conversely,with this arrangement, a relatively small resistance value for theturn-on resistance and turn-off resistance can be selectively providedusing one or more resistors, based on at least the state of thephase-leg 200, to provide a relatively faster switching speed forrelatively longer predetermined or selective time periods. In this way,the value of each turn-on resistance and turn-off resistance can beselected from a plurality of selectable resistance values, based on adesired optimized operation for switching speed in all output states402, 404, 406, 408, 410 or operating conditions of the phase leg 200.

In other non-limiting aspects, the output state 402, 404, 406, 408, 410of the phase-leg 200 need not be limited to being based solely on anoutput state 402, 404, 406, 408, 410 with respect to a voltage. Forexample, in non-limiting aspects, the output state 402, 404, 406, 408,410 of the phase-leg 200 can be based on a combination of an electricaloutput state 402, 404, 406, 408, 410 and a temperature state of thephase-leg 200. In other non-limiting aspects, the output state of thephase-leg 200 can be based on a combination of a voltage output state402, 404, 406, 408, 410 and a current state of the phase-leg 200. Instill other non-limiting aspects, the output state 402, 404, 406, 408,410 of the phase-leg 200 can be based on a combination of the voltageoutput state 402, 404, 406, 408, 410 and a voltage state of a switch210-220. In still other aspects, the output state 402, 404, 406, 408,410 of the phase-leg 200 can be determined based on a combination ofcurrent, voltage and temperature to determine the switching speed of oneor more switching devices in the power converter 100.

FIG. 7 depicts a method 700 of operating a phase-leg 200 of a powerconverter 100, the phase-leg 200 comprising set of switches 210-220communicatively coupled to a respective gate drive circuit 250 andswitchably responsive to a respective gate drive signal 57 from therespective gate drive circuit 250. The method 700 begins at 710 byproviding the respective gate drive signal 57 from each respective gatedrive circuit 250 to a corresponding switch 210-220 of the set ofswitches, and at 720 switchably transitioning an output state 402, 406,408, 410 of the phase-leg between one of a neutral state 402 having aneutral output voltage, a first state 406 having a first output voltage,and a second state 410 having a second output voltage, by selectivelyoperating the set of switches 210-220 based on the respective gate drivesignal 57. The method 700 can include determining the output state 402,404, 406, 408, 410 of the phase-leg 200 at 730. The method can alsoinclude, at 740 selectively changing at least one of a respectiveresistance and a current of a subset of the gate drive circuit 250 basedon the output state 402, 406, 408, 410 of the phase-leg 200.

The sequence depicted is for illustrative purposes only and is not meantto limit the method 700 in any way as it is understood that the portionsof the method can proceed in a different logical order, additional orintervening portions can be included, or described portions of themethod can be divided into multiple portions, or described portions ofthe method can be omitted without detracting from the described method.

Moreover, systems and methods as described herein can be applied duringa shutdown operation (e.g., a in response to a fault or trip condition).For example, all of the semiconductor devices can be configured toturn-off or trip immediately with a slower turn-off speed, therebyavoiding additional delay in at least some of the devices.

To the extent not already described, the different features andstructures of the various aspects can be used in combination with eachother as desired. That one feature cannot be illustrated in all of theaspects is not meant to be construed that it cannot be, but is done forbrevity of description. Thus, the various features of the differentaspects can be mixed and matched as desired to form new aspects, whetheror not the new aspects are expressly described. Combinations orpermutations of features described herein are covered by thisdisclosure.

Further aspects are provided by the subject matter of the followingclauses:

A power converter comprising: a set of switching elementscommunicatively coupled with a set of gate drive circuits, each gatedrive circuit configured to provide a respective signal to acorresponding switching element, the switching element being switchablyresponsive to the respective signal; and a controller module configuredto: control an output state of the power converter, and selectivelychange one of a respective resistance and a respective gate current ofthe gate drive circuits based on the output state of the powerconverter.

The power converter of any preceding clause, wherein the selectivelychanging one of a respective resistance and a respective gate current ofthe gate drive circuits results in a change to a switching speed of thecorresponding switching elements.

The power converter of any preceding clause, wherein the selectivelychanging a respective resistance of the gate drive circuits comprisesselectively operating a respective speed control switch in eachrespective gate drive circuit.

The power converter of any preceding clause, wherein the output state ofthe power converter is one of a positive voltage, a negative voltage,and a neutral voltage.

The power converter of any preceding clause, wherein the neutral voltageoutput state of the power converter is based on a zero-crossing of anoutput voltage of the power converter.

The power converter of any preceding clause, wherein when the outputstate of the power converter is determined to be a neutral voltage, thecontroller module is configured to selectively actuate a respectivespeed control switch in each respective gate drive circuit to increase aresistance of the respective gate drive circuit.

The power converter of any preceding clause, wherein when the outputstate of the power converter is one of a positive voltage and a negativevoltage, the controller module is configured to selectively actuate arespective speed control switch in each gate drive circuit of the subsetof gate drive circuits to decrease the resistance of the respective gatedrive circuit.

The power converter of any preceding clause, wherein the respectiveresistance of the respective gate drive circuit is changeable inresponse to an operation of a respective speed control switch therespective gate drive circuit.

The power converter of any preceding clause, wherein the controllermodule is further configured to determine at least one of a temperature,a voltage, a current, and a switching state, of at least a subset of theswitching elements, and to selectively change a respective resistance ofa corresponding subset of the gate drive circuits based on the outputstate of the power converter and on the determined at least one oftemperature, voltage, current, and switching state, of the at least asubset of the switching elements.

The power converter of any preceding clause, wherein the respectivesignal provided by each gate drive circuit is a DC voltage signal.

A method for operating a phase-leg of a power converter, the phase-legcomprising an output terminal, a set of input terminals, and a first setof switches disposed between the set of input terminals and the outputterminal, communicatively coupled to a respective gate control circuitof a set of gate control circuits, and switchably responsive to arespective drive signal from the respective gate control circuit, themethod comprising: providing a respective drive signal from each gatecontrol circuit to a corresponding switch of the first set of switches;switchably transitioning an output state of the phase-leg between one ofa neutral state having a neutral output voltage, a first state having afirst output voltage, and a second state having a second output voltage,by selectively operating the first set of switches based on therespective signal; and selectively changing one of a respectiveresistance and a respective current of a subset of the gate drivecircuits based on the output state of the phase-leg.

The method of any preceding clause, wherein the selectively changing oneof a respective resistance and a respective current of the subset of thegate drive circuits results in a change to a switching speed of acorresponding subset of switching elements.

The method of any preceding clause, wherein the selectively changing arespective resistance of the subset of the gate drive circuits comprisesselectively operating a respective speed control switch in a respectivegate driver circuit of the subset of the gate drive circuits to one ofincrease and decrease the resistance of the respective gate drivercircuit.

The method of any preceding clause, wherein the output state of thepower converter is one of a positive voltage, a negative voltage, and aneutral voltage.

The method of any preceding clause, wherein the neutral output state ofthe power converter is based on a zero-crossing of an output voltage ofthe power converter.

The method of any preceding clause, wherein when the output state of thepower converter is determined to be a neutral voltage, furthercomprising selectively actuating a respective speed control switch ineach gate drive circuit of the subset of gate drive circuits to increasea resistance of the respective gate drive circuit.

The method of any preceding clause, wherein when the output state of thepower converter is one of a positive voltage and a negative voltage,further comprising selectively actuating a respective speed controlswitch in each gate drive circuit of the subset of gate drive circuitsto decrease a resistance of the respective gate drive circuit.

The method of any preceding clause, wherein the selectively changing oneof a respective resistance and a respective current of a subset of thegate drive circuit includes operating a respective speed control switchin each gate drive circuit of the subset of gate drive circuits.

The method of any preceding clause, further comprising determining atleast one of a temperature, a voltage, a current, and a switching state,of at least a subset of the first set of switches; and selectivelychanging a respective resistance of a corresponding subset of the gatedrive circuits based on the output state of the phase-leg and thedetermined at least one of temperature, voltage, current, and switchingstate, of at least a subset of the first set of switches.

The method of any preceding clause, wherein the respective signalprovided by each gate drive circuit is a DC voltage signal.

What is claimed is:
 1. A power converter comprising: a set of switchingelements communicatively coupled with a set of gate drive circuits, eachgate drive circuit configured to provide a respective signal to acorresponding switching element, the corresponding switching elementbeing switchably responsive to the respective signal; and a controllermodule configured to: control an output state of the power converter,and selectively change one of a respective resistance and a respectivegate current of the gate drive circuits based on the output state of thepower converter; wherein the output state of the power converter is oneof a first voltage output state, a second voltage output state, and aneutral voltage output state.
 2. The power converter of claim 1, whereinthe selectively changing one of a respective resistance and a respectivegate current of the gate drive circuits results in a change to aswitching speed of the corresponding switching elements.
 3. The powerconverter of claim 1, wherein the selectively changing a respectiveresistance of the gate drive circuits comprises selectively operating arespective speed control switch in each respective gate drive circuit.4. The power converter of claim 1, wherein the neutral voltage outputstate further includes at least one of a first intermediate neutralstate and a second intermediate neutral state.
 5. The power converter ofclaim 4, wherein, in response to a desired first voltage output state ofthe power converter, the controller module is further configured toselectively change one of a respective resistance and a respective gatecurrent of the gate drive circuits based on the output state of thepower converter to operably transition the output state of the powerconverter from the neutral voltage output state to the firstintermediate neutral state.
 6. The power converter of claim 5, whereinthe controller module is further configured to selectively change one ofa respective resistance and a respective gate current of the gate drivecircuits based on the output state of the power converter to operablytransition the output state of the power converter from the firstintermediate neutral state to the first voltage output state.
 7. Thepower converter of claim 6, wherein operably transitioning from theneutral voltage output state to the first intermediate neutral state,and further to the first voltage output state, operably reduces voltagestress across a power converter output switch.
 8. The power converter ofclaim 4, wherein, in response to a desired second voltage output stateof the power converter, the controller module is further configured toselectively change one of a respective resistance and a respective gatecurrent of the gate drive circuits based on the output state of thepower converter to operably transition the output state of the powerconverter from the neutral voltage output state to the secondintermediate neutral state.
 9. The power converter of claim 8, whereinthe controller module is further configured to selectively change one ofa respective resistance and a respective gate current of the gate drivecircuits based on the output state of the power converter to operablytransition the output state of the power converter from the secondintermediate neutral state to the second voltage output state.
 10. Thepower converter of claim 9, wherein operably transitioning from theneutral state to the second intermediate neutral state, and further tothe second voltage output state, operably reduces voltage stress acrossa power converter output switch.
 11. The power converter of claim 4,wherein selectively changing one of a respective resistance and arespective gate current of the gate drive circuits based on the outputstate of the power converter, wherein the output state is at least oneof a first intermediate neutral state and a second intermediate neutralstate enables at least one of charging or discharging a current at apower converter output switch.
 12. The power converter of claim 1,further comprising a modulator communicatively coupled with a set ofphase legs of the power converter.
 13. The power converter of claim 12,wherein the controller module is included with the modulator.
 14. Thepower converter of claim 1, wherein the controller module is furtherconfigured to determine at least one of a temperature, a voltage, acurrent, and a switching state of at least a subset of the switchingelements, and to selectively change a respective resistance of acorresponding subset of the gate drive circuits based on the outputstate of the power converter and on the determined at least one oftemperature, voltage, current, and switching state of the at least asubset of the switching elements.
 15. A method for operating a phase-legof a power converter, the phase-leg comprising an output terminal, a setof input terminals, and a set of switches disposed between the set ofinput terminals and the output terminal, communicatively coupled to arespective gate control circuit of a set of gate control circuits, andswitchably responsive to a respective drive signal from the respectivegate control circuit, the method comprising: providing the respectivedrive signal from each gate control circuit to a corresponding switch ofthe set of switches; switchably transitioning an output state of thephase-leg between one of a neutral state having a neutral outputvoltage, a positive state having a positive output voltage, and anegative state having a negative output voltage, by selectivelyoperating the set of switches based on the respective drive signal; andselectively changing one of a respective resistance and a respectivecurrent of a subset of the gate drive circuits based on the output stateof the phase-leg.
 16. The method of claim 15, wherein the selectivelychanging one of a respective resistance and a respective current of thesubset of the gate drive circuits results in a change to a switchingspeed of a corresponding subset of switches.
 17. The method of claim 15,wherein the selectively changing a respective resistance of the subsetof the gate drive circuits comprises selectively operating a respectivespeed control switch in a respective gate drive circuit of the subset ofthe gate drive circuits to one of increase or decrease the resistance ofthe respective gate drive circuit.
 18. The method of claim 15, whereinswitchably transitioning an output state of the phase-leg between theneutral state and the positive state further includes selectivelyoperating the set of switches based on the respective drive signal totransition from the neutral state to a first intermediate neutral state,and from the first intermediate neutral state to the positive state. 19.The method of claim 18, wherein transitioning from the neutral state toa first intermediate neutral state, and from the first intermediateneutral state to the positive state operably reduces voltage stressacross at least a subset of the switches.
 20. The method of claim 18,wherein switchably transitioning an output state of the phase-legbetween the neutral state and the negative state further includesselectively operating the set of switches based on the respective drivesignal to transition from the neutral state to a second intermediateneutral state, and from the second intermediate neutral state to thenegative state.